source: rtems-docs/c-user/config/general.rst @ cf9f212

.. SPDX-License-Identifier: CC-BY-SA-4.0

.. Copyright (C) 2020, 2021 embedded brains GmbH (http://www.embedded-brains.de)
.. Copyright (C) 1988, 2022 On-Line Applications Research Corporation (OAR)

.. This file is part of the RTEMS quality process and was automatically
.. generated.  If you find something that needs to be fixed or
.. worded better please post a report or patch to an RTEMS mailing list
.. or raise a bug report:
..
.. https://www.rtems.org/bugs.html
..
.. For information on updating and regenerating please refer to the How-To
.. section in the Software Requirements Engineering chapter of the
.. RTEMS Software Engineering manual.  The manual is provided as a part of
.. a release.  For development sources please refer to the online
.. documentation at:
..
.. https://docs.rtems.org

.. Generated from spec:/acfg/if/group-general

General System Configuration
============================

This section describes general system configuration options.

.. Generated from spec:/acfg/if/dirty-memory

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_DIRTY_MEMORY

.. _CONFIGURE_DIRTY_MEMORY:

CONFIGURE_DIRTY_MEMORY
----------------------

.. rubric:: CONSTANT:

``CONFIGURE_DIRTY_MEMORY``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the memory areas used for
the RTEMS Workspace and the C Program Heap are dirtied with a ``0xCF`` byte
pattern during system initialization.

.. rubric:: NOTES:

Dirtying memory can add significantly to system initialization time.  It may
assist in finding code that incorrectly assumes the contents of free memory
areas is cleared to zero during system initialization.  In case
:ref:`CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY` is also defined, then the
memory is first dirtied and then zeroed.

See also :ref:`CONFIGURE_MALLOC_DIRTY`.

.. Generated from spec:/acfg/if/disable-bsp-settings

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_DISABLE_BSP_SETTINGS

.. _CONFIGURE_DISABLE_BSP_SETTINGS:

CONFIGURE_DISABLE_BSP_SETTINGS
------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_DISABLE_BSP_SETTINGS``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the optional BSP provided
settings listed below are disabled.

The optional BSP provided default values for the following application
configuration options are disabled:

* :ref:`CONFIGURE_IDLE_TASK_BODY`

* :ref:`CONFIGURE_IDLE_TASK_STACK_SIZE`

* :ref:`CONFIGURE_INTERRUPT_STACK_SIZE`

The optional BSP provided initial extension set is disabled (see
:term:`initial extension sets`).  The optional BSP provided
prerequisite IO device drivers are disabled (see
Device Driver Configuration).  The optional BSP provided support for
:c:func:`sbrk` is disabled.

This configuration option provides an all or nothing choice with respect to
the optional BSP provided settings.

.. Generated from spec:/acfg/if/disable-newlib-reentrancy

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_DISABLE_NEWLIB_REENTRANCY

.. _CONFIGURE_DISABLE_NEWLIB_REENTRANCY:

CONFIGURE_DISABLE_NEWLIB_REENTRANCY
-----------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_DISABLE_NEWLIB_REENTRANCY``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the Newlib reentrancy
support per thread is disabled and a global reentrancy structure is used.

.. rubric:: NOTES:

You can enable this option to reduce the size of the :term:`TCB`.  Use this
option with care, since it can lead to race conditions and undefined system
behaviour.  For example, :c:macro:`errno` is no longer a thread-local
variable if this option is enabled.

.. Generated from spec:/acfg/if/executive-ram-size

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_EXECUTIVE_RAM_SIZE

.. _CONFIGURE_EXECUTIVE_RAM_SIZE:

CONFIGURE_EXECUTIVE_RAM_SIZE
----------------------------

.. rubric:: CONSTANT:

``CONFIGURE_EXECUTIVE_RAM_SIZE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

If this configuration option is undefined, then the RTEMS Workspace and task
stack space size is calculated by ``<rtems/confdefs.h>`` based on the values
configuration options.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the RTEMS Workspace size in
bytes.

.. rubric:: NOTES:

This is an advanced configuration option.  Use it only if you know exactly
what you are doing.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to
  `UINTPTR_MAX <https://en.cppreference.com/w/c/types/integer>`_.

* The value of the configuration option shall be less than or equal to a
  BSP-specific and application-specific value which depends on the size of the
  memory available to the application.

.. Generated from spec:/acfg/if/extra-task-stacks

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_EXTRA_TASK_STACKS
.. index:: memory for task tasks

.. _CONFIGURE_EXTRA_TASK_STACKS:

CONFIGURE_EXTRA_TASK_STACKS
---------------------------

.. rubric:: CONSTANT:

``CONFIGURE_EXTRA_TASK_STACKS``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 0.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the number of bytes the
applications wishes to add to the task stack requirements calculated by
``<rtems/confdefs.h>``.

.. rubric:: NOTES:

This parameter is very important.  If the application creates tasks with
stacks larger then the minimum, then that memory is **not** accounted for by
``<rtems/confdefs.h>``.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be small enough so that the task
  stack space calculation carried out by ``<rtems/confdefs.h>`` does not
  overflow an integer of type `uintptr_t
  <https://en.cppreference.com/w/c/types/integer>`_.

.. Generated from spec:/acfg/if/initial-extensions

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_INITIAL_EXTENSIONS

.. _CONFIGURE_INITIAL_EXTENSIONS:

CONFIGURE_INITIAL_EXTENSIONS
----------------------------

.. rubric:: CONSTANT:

``CONFIGURE_INITIAL_EXTENSIONS``

.. rubric:: OPTION TYPE:

This configuration option is an initializer define.

.. rubric:: DEFAULT VALUE:

The default value is the empty list.

.. rubric:: DESCRIPTION:

The value of this configuration option is used to initialize the table of
initial user extensions.

.. rubric:: NOTES:

The value of this configuration option is placed before the entries of
:c:macro:`BSP_INITIAL_EXTENSION` and after the entries of all other
initial user extensions.

.. rubric:: CONSTRAINTS:

The value of the configuration option shall be a list of initializers for
structures of type :c:type:`rtems_extensions_table`.

.. Generated from spec:/acfg/if/interrupt-stack-size

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_INTERRUPT_STACK_SIZE
.. index:: interrupt stack size

.. _CONFIGURE_INTERRUPT_STACK_SIZE:

CONFIGURE_INTERRUPT_STACK_SIZE
------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_INTERRUPT_STACK_SIZE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

If the :ref:`CONFIGURE_DISABLE_BSP_SETTINGS` configuration option is not defined and
:c:macro:`BSP_INTERRUPT_STACK_SIZE` is provided by the
:term:`BSP`, then the default value is defined by
:c:macro:`BSP_INTERRUPT_STACK_SIZE`, otherwise the default value is
:c:macro:`CPU_STACK_MINIMUM_SIZE`.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the size of an interrupt stack
in bytes.

.. rubric:: NOTES:

There is one interrupt stack available for each configured processor
(:ref:`CONFIGURE_MAXIMUM_PROCESSORS`).  The interrupt stack areas are
statically allocated in a special linker section (``.rtemsstack.interrupt``).
The placement of this linker section is BSP-specific.

Some BSPs use the interrupt stack as the initialization stack which is used
to perform the sequential system initialization before the multithreading
is started.

The interrupt stacks are covered by the stack checker, see
:ref:`CONFIGURE_STACK_CHECKER_ENABLED`.  However, using a too small interrupt stack
size may still result in undefined behaviour.

In releases before RTEMS 5.1 the default value was
:ref:`CONFIGURE_MINIMUM_TASK_STACK_SIZE` instead of
:c:macro:`CPU_STACK_MINIMUM_SIZE`.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to a
  BSP-specific and application-specific minimum value.

* The value of the configuration option shall be small enough so that the
  interrupt stack area calculation carried out by ``<rtems/confdefs.h>`` does
  not overflow an integer of type `size_t
  <https://en.cppreference.com/w/c/types/size_t>`_.

* The value of the configuration option shall be aligned according to
  :c:macro:`CPU_INTERRUPT_STACK_ALIGNMENT`.

.. Generated from spec:/acfg/if/malloc-dirty

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MALLOC_DIRTY

.. _CONFIGURE_MALLOC_DIRTY:

CONFIGURE_MALLOC_DIRTY
----------------------

.. rubric:: CONSTANT:

``CONFIGURE_MALLOC_DIRTY``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then each memory area returned
by C Program Heap allocator functions such as :c:func:`malloc` is dirtied
with a ``0xCF`` byte pattern before it is handed over to the application.

.. rubric:: NOTES:

The dirtying performed by this option is carried out for each successful
memory allocation from the C Program Heap in contrast to
:ref:`CONFIGURE_DIRTY_MEMORY` which dirties the memory only once during the
system initialization.

.. Generated from spec:/acfg/if/max-file-descriptors

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MAXIMUM_FILE_DESCRIPTORS
.. index:: maximum file descriptors

.. _CONFIGURE_MAXIMUM_FILE_DESCRIPTORS:

CONFIGURE_MAXIMUM_FILE_DESCRIPTORS
----------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MAXIMUM_FILE_DESCRIPTORS``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 3.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the maximum number of file
like objects that can be concurrently open.

.. rubric:: NOTES:

The default value of three file descriptors allows RTEMS to support standard
input, output, and error I/O streams on :file:`/dev/console`.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to
  `SIZE_MAX <https://en.cppreference.com/w/c/types/limits>`_.

* The value of the configuration option shall be less than or equal to a
  BSP-specific and application-specific value which depends on the size of the
  memory available to the application.

.. Generated from spec:/acfg/if/max-processors

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MAXIMUM_PROCESSORS

.. _CONFIGURE_MAXIMUM_PROCESSORS:

CONFIGURE_MAXIMUM_PROCESSORS
----------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MAXIMUM_PROCESSORS``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 1.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the maximum number of
processors an application intends to use.  The number of actually available
processors depends on the hardware and may be less.  It is recommended to use
the smallest value suitable for the application in order to save memory.
Each processor needs an IDLE task stack and interrupt stack for example.

.. rubric:: NOTES:

If there are more processors available than configured, the rest will be
ignored.

This configuration option is only evaluated in SMP configurations of RTEMS
(e.g. RTEMS was built with the SMP build configuration option enabled).
In all other configurations it has no effect.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to one.

* The value of the configuration option shall be less than or equal to
  :c:macro:`CPU_MAXIMUM_PROCESSORS`.

.. Generated from spec:/acfg/if/max-thread-name-size

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MAXIMUM_THREAD_NAME_SIZE
.. index:: maximum thread name size

.. _CONFIGURE_MAXIMUM_THREAD_NAME_SIZE:

CONFIGURE_MAXIMUM_THREAD_NAME_SIZE
----------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MAXIMUM_THREAD_NAME_SIZE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 16.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the maximum thread name size
including the terminating ``NUL`` character.

.. rubric:: NOTES:

The default value was chosen for Linux compatibility, see
`pthread_setname_np() <http://man7.org/linux/man-pages/man3/pthread_setname_np.3.html>`_.

The size of the thread control block is increased by the maximum thread name
size.

This configuration option is available since RTEMS 5.1.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to
  `SIZE_MAX <https://en.cppreference.com/w/c/types/limits>`_.

* The value of the configuration option shall be less than or equal to a
  BSP-specific and application-specific value which depends on the size of the
  memory available to the application.

.. Generated from spec:/acfg/if/memory-overhead

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MEMORY_OVERHEAD

.. _CONFIGURE_MEMORY_OVERHEAD:

CONFIGURE_MEMORY_OVERHEAD
-------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MEMORY_OVERHEAD``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 0.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the number of kilobytes the
application wishes to add to the RTEMS Workspace size calculated by
``<rtems/confdefs.h>``.

.. rubric:: NOTES:

This configuration option should only be used when it is suspected that a bug
in ``<rtems/confdefs.h>`` has resulted in an underestimation.  Typically the
memory allocation will be too low when an application does not account for
all message queue buffers or task stacks, see
:ref:`CONFIGURE_MESSAGE_BUFFER_MEMORY`.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to a
  BSP-specific and application-specific value which depends on the size of the
  memory available to the application.

* The value of the configuration option shall be small enough so that the RTEMS
  Workspace size calculation carried out by ``<rtems/confdefs.h>`` does not
  overflow an integer of type `uintptr_t
  <https://en.cppreference.com/w/c/types/integer>`_.

.. Generated from spec:/acfg/if/message-buffer-memory

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MESSAGE_BUFFER_MEMORY
.. index:: configure message queue buffer memory
.. index:: CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE
.. index:: memory for a single message queue's buffers

.. _CONFIGURE_MESSAGE_BUFFER_MEMORY:

CONFIGURE_MESSAGE_BUFFER_MEMORY
-------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MESSAGE_BUFFER_MEMORY``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 0.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the number of bytes reserved
for message queue buffers in the RTEMS Workspace.

.. rubric:: NOTES:

The configuration options :ref:`CONFIGURE_MAXIMUM_MESSAGE_QUEUES` and
:ref:`CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES` define only how many message
queues can be created by the application.  The memory for the message
buffers is configured by this option.  For each message queue you have to
reserve some memory for the message buffers.  The size depends on the
maximum number of pending messages and the maximum size of the messages of
a message queue.  Use the ``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()`` macro
to specify the message buffer memory for each message queue and sum them up
to define the value for ``CONFIGURE_MAXIMUM_MESSAGE_QUEUES``.

The interface for the ``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()`` help
macro is as follows:

.. code-block:: c

    CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( max_messages, max_msg_size )

Where ``max_messages`` is the maximum number of pending messages and
``max_msg_size`` is the maximum size in bytes of the messages of the
corresponding message queue.  Both parameters shall be compile time
constants.  Not using this help macro (e.g. just using
``max_messages * max_msg_size``) may result in an underestimate of the
RTEMS Workspace size.

The following example illustrates how the
``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()`` help macro can be used to assist in
calculating the message buffer memory required.  In this example, there are
two message queues used in this application.  The first message queue has a
maximum of 24 pending messages with the message structure defined by the
type ``one_message_type``.  The other message queue has a maximum of 500
pending messages with the message structure defined by the type
``other_message_type``.

.. code-block:: c

    #define CONFIGURE_MESSAGE_BUFFER_MEMORY ( \
        CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
          24, \
          sizeof( one_message_type ) \
        ) \
        + CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
          500, \
          sizeof( other_message_type ) \
        ) \
      )

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to a
  BSP-specific and application-specific value which depends on the size of the
  memory available to the application.

* The value of the configuration option shall be small enough so that the RTEMS
  Workspace size calculation carried out by ``<rtems/confdefs.h>`` does not
  overflow an integer of type `uintptr_t
  <https://en.cppreference.com/w/c/types/integer>`_.

.. Generated from spec:/acfg/if/microseconds-per-tick

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MICROSECONDS_PER_TICK
.. index:: clock tick quantum
.. index:: tick quantum

.. _CONFIGURE_MICROSECONDS_PER_TICK:

CONFIGURE_MICROSECONDS_PER_TICK
-------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MICROSECONDS_PER_TICK``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 10000.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the length of time in
microseconds between clock ticks (clock tick quantum).

When the clock tick quantum value is too low, the system will spend so much
time processing clock ticks that it does not have processing time available
to perform application work. In this case, the system will become
unresponsive.

The lowest practical time quantum varies widely based upon the speed of the
target hardware and the architectural overhead associated with
interrupts. In general terms, you do not want to configure it lower than is
needed for the application.

The clock tick quantum should be selected such that it all blocking and
delay times in the application are evenly divisible by it. Otherwise,
rounding errors will be introduced which may negatively impact the
application.

.. rubric:: NOTES:

This configuration option has no impact if the Clock Driver is not
configured, see :ref:`CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`.

There may be Clock Driver specific limits on the resolution or maximum value
of a clock tick quantum.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to a
  value defined by the :term:`Clock Driver`.

* The value of the configuration option shall be less than or equal to a value
  defined by the :term:`Clock Driver`.

* The resulting clock ticks per second should be an integer.

.. Generated from spec:/acfg/if/min-task-stack-size

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_MINIMUM_TASK_STACK_SIZE
.. index:: minimum task stack size

.. _CONFIGURE_MINIMUM_TASK_STACK_SIZE:

CONFIGURE_MINIMUM_TASK_STACK_SIZE
---------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_MINIMUM_TASK_STACK_SIZE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is :c:macro:`CPU_STACK_MINIMUM_SIZE`.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the minimum stack size in
bytes for every user task or thread in the system.

.. rubric:: NOTES:

Adjusting this parameter should be done with caution.  Examining the actual
stack usage using the stack checker usage reporting facility is recommended
(see also :ref:`CONFIGURE_STACK_CHECKER_ENABLED`).

This parameter can be used to lower the minimum from that recommended. This
can be used in low memory systems to reduce memory consumption for
stacks. However, this shall be done with caution as it could increase the
possibility of a blown task stack.

This parameter can be used to increase the minimum from that
recommended. This can be used in higher memory systems to reduce the risk
of stack overflow without performing analysis on actual consumption.

By default, this configuration parameter defines also the minimum stack
size of POSIX threads.  This can be changed with the
:ref:`CONFIGURE_MINIMUM_POSIX_THREAD_STACK_SIZE`
configuration option.

In releases before RTEMS 5.1 the ``CONFIGURE_MINIMUM_TASK_STACK_SIZE`` was
used to define the default value of :ref:`CONFIGURE_INTERRUPT_STACK_SIZE`.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be small enough so that the task
  stack space calculation carried out by ``<rtems/confdefs.h>`` does not
  overflow an integer of type `uintptr_t
  <https://en.cppreference.com/w/c/types/integer>`_.

* The value of the configuration option shall be greater than or equal to a
  BSP-specific and application-specific minimum value.

.. Generated from spec:/acfg/if/stack-checker-enabled

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_STACK_CHECKER_ENABLED

.. _CONFIGURE_STACK_CHECKER_ENABLED:

CONFIGURE_STACK_CHECKER_ENABLED
-------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_STACK_CHECKER_ENABLED``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the stack checker is
enabled.

.. rubric:: NOTES:

The stack checker performs run-time stack bounds checking.  This increases
the time required to create tasks as well as adding overhead to each context
switch.

In 4.9 and older, this configuration option was named ``STACK_CHECKER_ON``.

.. Generated from spec:/acfg/if/ticks-per-time-slice

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_TICKS_PER_TIMESLICE
.. index:: ticks per timeslice

.. _CONFIGURE_TICKS_PER_TIMESLICE:

CONFIGURE_TICKS_PER_TIMESLICE
-----------------------------

.. rubric:: CONSTANT:

``CONFIGURE_TICKS_PER_TIMESLICE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 50.

.. rubric:: DESCRIPTION:

The value of this configuration option defines the length of the timeslice
quantum in ticks for each task.

.. rubric:: NOTES:

This configuration option has no impact if the Clock Driver is not
configured, see :ref:`CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`.

.. rubric:: CONSTRAINTS:

The following constraints apply to this configuration option:

* The value of the configuration option shall be greater than or equal to zero.

* The value of the configuration option shall be less than or equal to
  `UINT32_MAX <https://en.cppreference.com/w/c/types/integer>`_.

.. Generated from spec:/acfg/if/unified-work-areas

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_UNIFIED_WORK_AREAS
.. index:: unified work areas
.. index:: separate work areas
.. index:: RTEMS Workspace
.. index:: C Program Heap

.. _CONFIGURE_UNIFIED_WORK_AREAS:

CONFIGURE_UNIFIED_WORK_AREAS
----------------------------

.. rubric:: CONSTANT:

``CONFIGURE_UNIFIED_WORK_AREAS``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then there will be separate memory
pools for the RTEMS Workspace and C Program Heap.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the RTEMS Workspace and
the C Program Heap will be one pool of memory.

.. rubric:: NOTES:

Having separate pools does have some advantages in the event a task blows a
stack or writes outside its memory area. However, in low memory systems the
overhead of the two pools plus the potential for unused memory in either
pool is very undesirable.

In high memory environments, this is desirable when you want to use the
:ref:`ConfigUnlimitedObjects` option.  You will be able to create objects
until you run out of all available memory rather then just until you run out
of RTEMS Workspace.

.. Generated from spec:/acfg/if/unlimited-allocation-size

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_UNLIMITED_ALLOCATION_SIZE

.. _CONFIGURE_UNLIMITED_ALLOCATION_SIZE:

CONFIGURE_UNLIMITED_ALLOCATION_SIZE
-----------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_UNLIMITED_ALLOCATION_SIZE``

.. rubric:: OPTION TYPE:

This configuration option is an integer define.

.. rubric:: DEFAULT VALUE:

The default value is 8.

.. rubric:: DESCRIPTION:

If :ref:`CONFIGURE_UNLIMITED_OBJECTS` is defined, then the value of this
configuration option defines the default objects maximum of all object
classes supporting :ref:`ConfigUnlimitedObjects` to
``rtems_resource_unlimited( CONFIGURE_UNLIMITED_ALLOCATION_SIZE )``.

.. rubric:: NOTES:

By allowing users to declare all resources as being unlimited the user can
avoid identifying and limiting the resources used.

The object maximum of each class can be configured also individually using
the :c:func:`rtems_resource_unlimited` macro.

.. rubric:: CONSTRAINTS:

The value of the configuration option shall meet the constraints of all object
classes to which it is applied.

.. Generated from spec:/acfg/if/unlimited-objects

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_UNLIMITED_OBJECTS

.. _CONFIGURE_UNLIMITED_OBJECTS:

CONFIGURE_UNLIMITED_OBJECTS
---------------------------

.. rubric:: CONSTANT:

``CONFIGURE_UNLIMITED_OBJECTS``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then unlimited objects are used
by default.

.. rubric:: NOTES:

When using unlimited objects, it is common practice to also specify
:ref:`CONFIGURE_UNIFIED_WORK_AREAS` so the system operates with a single pool
of memory for both RTEMS Workspace and C Program Heap.

This option does not override an explicit configuration for a particular
object class by the user.

See also :ref:`CONFIGURE_UNLIMITED_ALLOCATION_SIZE`.

.. Generated from spec:/acfg/if/verbose-system-init

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_VERBOSE_SYSTEM_INITIALIZATION

.. _CONFIGURE_VERBOSE_SYSTEM_INITIALIZATION:

CONFIGURE_VERBOSE_SYSTEM_INITIALIZATION
---------------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_VERBOSE_SYSTEM_INITIALIZATION``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the system initialization
is verbose.

.. rubric:: NOTES:

You may use this feature to debug system initialization issues.  The
:c:func:`printk` function is used to print the information.

.. Generated from spec:/acfg/if/zero-workspace-automatically

.. raw:: latex

    \clearpage

.. index:: CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY
.. index:: clear C Program Heap
.. index:: clear RTEMS Workspace
.. index:: zero C Program Heap
.. index:: zero RTEMS Workspace

.. _CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY:

CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY
--------------------------------------

.. rubric:: CONSTANT:

``CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY``

.. rubric:: OPTION TYPE:

This configuration option is a boolean feature define.

.. rubric:: DEFAULT CONFIGURATION:

If this configuration option is undefined, then the described feature is not
enabled.

.. rubric:: DESCRIPTION:

In case this configuration option is defined, then the memory areas used for
the RTEMS Workspace and the C Program Heap are zeroed with a ``0x00`` byte
pattern during system initialization.

.. rubric:: NOTES:

Zeroing memory can add significantly to the system initialization time. It is
not necessary for RTEMS but is often assumed by support libraries.  In case
:ref:`CONFIGURE_DIRTY_MEMORY` is also defined, then the memory is first
dirtied and then zeroed.